There have been known conventional flat batteries having a positive electrode material and a negative electrode material provided between a closed-bottom tubular exterior can and a sealing can provided to cover the opening of the exterior can. As disclosed by JP-A 2008-103109, one of such known flat batteries includes a positive electrode ring that holds a positive electrode pellet and is welded to the inside of a positive electrode can by resistance welding or laser welding. In this way, the positive electrode ring can be prevented from moving with respect to the positive electrode can and the positive electrode can and the positive electrode ring can be contacted in a stable manner.